Boiler for digesting wood for paper-pulp



(No Model.)

G. E. MARSHALL.

BOILER FOR DIGESTING WOOD FOR PAPER PULP. No. 286,031. Patented 001;. 2, 1883.

UNITED STATES PATENT O FICE.

enonen MARSHALL, or 'rnnnnns FALLS, M'AssAcHUsnr'rs' BOILERFOR DIGESTING WOOD-FOR PAPER-PULP.

srncrrrcnrion forming To all whom it may concern.-

Be it knownthat I, GEORG E. MABsHALL a citizen of the United States, residing at Turners Falls, in the county of Franklin and Commonwealth of Massachusetts, have invented a new and useful Improvement ;in B0ilers for Digesting. Wood into .Pulp tobe used in the Manufacture of Paper. Y

My invention relates, principally, to the manufacture of wood pulp forzpaper by thechemical process and it consists of improvements in the construction and operation of the digester, in'which the chipped wood .is reduced to the soft or pulpy state to .be worked.

The manufacture of wood pulp by the chemical process has, from its invention down to the present time, been attended by very disagreeable and expensive features. 'It is a wellknown fact-that all wood-pulp digesters, of

whatever description, 'leak'more or less when a certain pressure has been attained. Gener-.

ally, when the pressure due to the steam heat has reached sixtypounds per square inch, the digester begins to leak, and as the pressure is increased to one hundred or more pounds'th e leakage is also increased, and it frequently.

happens that as much as one fourth or onethird of all the boiling liquors in -the digester are lost in this manner, and necessitates charging the 'digester with an excess: of alkaline liq uor. The leakage'isforced out through the riveted seams of the digester in the form of a fine spray and charges the surrounding atmosphere with an exceedingly offensive and suf-' of steel in orderto have a4:lose-grained-sur face at the seams. But none of these various methods have'proved'successful in prevent--.

ing the leakage; and it is a well-knownfact that wood-digesters will be run but a few weeks without recalking and replacing rlvets,

and the utmost. care and skill of the iboile'm part of Letters Patent lie-286,031, dated October 2, 1883. Application filed July 23, 1883. (No modem maker hasfailed toprodnce digesters that will not leak at or through the seams. The filling and 'dischargingjof the digester two or three times daily, thus exposing it to temper aturesvarying. from to 320 Fahrenheit, prodnces expansion and contraction sufficient to cause the iron or-steel-plates to creep at the seams, and thus wear away the calking. When the pressure has reached a lcertaln point, 'it opens the seamssufficiently to allow the escape ofthe very volatile liquor composed of the caustic alkali and other products generatedintheprocessofthedisintegration ofwood.

Even'in the" pulping of wood plain, without chemicals, the escape of thepinic, pyro1igne-- ous, and other acids is annoying and injurious.

By my inventionI overcome all these difiieulties, and have constructed and successfully operated for several months wood-digesters that are perfectlyitight, not leaking at all, and have therefore changed the manufacture of chemical woodpulp from the most disagreea -ble, offensive, and wastefulprocess know'n'in the whole'artof paper-making to. a pleasant,

safe, and, economical system, always produc ingsure results, and worked with. more ease and comfort than the ordinary process of boiling rag stock.

. The accompanying drawingillustrates myinvention, 1 and forms part, of I this specifica' tion. y

, To make my specificatidn plainer, I proceed to give' .a description of the digesters as Ihave made and-used them without, however, being bound .by fixed measurements or figureslgiven.

. The, drawing represents a stationary'up right wooddigester-witli its appurtenances. v A, the digester, .is six feet in .dlameter and- 'sixteeu..feet long, made from one-half inch iron or. steel 'boiler-plates--allseams double riveted. f

- B, the outer shell or jacket, is six-feet and eight inches in diameter, and connected to the digester at a distance of from eight to twelve inches below the top Qf,the same, the upper 'eu'defjacketB being drawn in to a diameter two inches greater than thelgliameterf of the.

.digester, for the purposeof placing the digesterwithin the jacket. I

ICC)

.A wrought-ironring, one inch thick by four orfive wide, and made in sections, fills the space between the end of "the jacket and-"the 'digester, and two rows of rivets are put through the j acket ring and the digester. Four screws, 1?, one and one-eighth inch diameter,

are put through the lower end of the jacket with a reenforcing plate to assist in support iug the weight of the digester.

The jacket B shouldibe covered with felt-' ing, asbestus, or some other non-conducting substance, to preserve a uniformity of temperature and to prevent undue condensation in cold weather. It is also connected with the digester by suitable stay-bolts to guard against the explosion .of the one or the collapse of the other.

The digester is provided with the usual per forated false bottom,11l,extending across at a heightof from ten to twelve inches from the bottom, of the 'digester.

O is'a gate operated by a rod "passing up through the digeter, with a hand-wheel and screw at top, shutting over the end of the blow-off pipe D, and is used to prevent the wood from entering the pipe leading to the blow-oif valve at D while the 'wood is being treated. The blow-oif valve is at D, used to discharge the contents of the digester, and is connected to a heavy eight-inch wrought-iron pipe passing through a stuffing-box in the jacket B, and screwed into a heavy wroughtiron ring riveted inside of the digestenas shown in the drawing.

G is a two inch iron pipe connecting the top' and bottom of the digester, and is used while the steam-pressureis being raised to conduct the liquor from the bottom to the top of the 1 digester for the purpose of removing any pulp that mayhave passed, through the perforated .space under the false bottom 40 raised, .5

false bottom, it being important to keep the clear of fiber; and-as the pressure is. greater at the bottom of the digester than at :the top until the full pressure required is attained, the opening of the valve inthis pipe will cause the liquor to circulate from the bottomto the top of the di-' gester, carrying with it any fiber remaining in the liquor. This "pipe may also 'be used to circulate the hot liquor from the bottom to the topof the digester while the pressure is being is a twoinch pipe. extending upward from nearthe top of the jacket, having an arm extending across and down into the top of the 7' digester, and contains a pressure-valve, I,

for the purpose of regulating the steam-press ure in the space between the jacket and the digester, and for relieving the pressure on the outside of the digester when its contents are 7 being discharged through the blow-oft valve D,-'insuring the digester from the danger of collapsing from outside strain by pressure in the jacket. This pressure-valve P 'is controlled by weights, which can be regulated according tothe indications of thesteamgages K K, one of which connects with the jacket and the other with the digcster. The steam for treatingthe stock in the digester is admitted through a pipe, H, directly to the alkaline, liquor, all attempts to treat the stock by the heat of the steam within the jacket proving insuflicient, it not penetrating to the center of the digester, and leaving a core of uncooked wood inthe middle.

I is an'inch-and-a-half pipe for conveying steam into the space between the jacket and the digester, for the purpose of maintaining steam in thejjacket, which is a very great convenience over the former way of washing the digester, with coldwater.

I am aware that jackets have beenplaeed on digestersland boilers for some purposes,

but not in the way nor for the attainment of the same objects as mine.

,What I claim is I v 1. A digester for wood pulp, constructed substantially as described, whereby the press ure of theboiling liquor at the seams or laps of the digester is equalized bythe pressure of the steam in the space between the digester and itssurrnuuding iaeket:

2. The combination ofthc hlow ofi' .valve T) and its, connections with the digester, substantially as described:

- 3. The combination of-the pipe Fand itspressure-valve with the digester, substauti ally as r .4. The combination of the eirculating'pipe G with the digester, substantially as described.

- 51 The combination'of the hot-water pipe 0 with the digester, substantially as described; 1. GEORGE EJWARSHALL.

lVitnesses:

Y J AMnsS. Grammar], JVILLIAM 1); RussELL. 

